Hyaluronic acid is a high molecular weight polysaccharide having a high water retention capability and has drawn attention as a very important extracellular matrix component in the skin (Shingo SAKAI, Shintaro INOUE, Metabolism of Hyaluronic Acid and Wrinkle Formation, Fragrance Journal, Fragrance Journal Ltd., vol. 26, no. 4, 49-58, Apr. 15, 1998).
Further, hyaluronic acid has been known to have many functions such as maintaining cells, retaining smoothness and suppleness of the skin, rendering the skin resistant to external force such as mechanical force and preventing the infection with pathogenic bacteria (BIO INDUSTRY, CMC Co., Ltd, vol. 8 no. 5, 66(346)-68(346), May 1, 1991).
On the other hand, it is reported that the intensity of the hyaluronic acid staining observed in the intercellular part of the epidermis decreases with aging (Ludger J. M. Meyer and Robert Stern, Age-Dependent Changes of Hyaluronan in Human Skin, The Journal of Investigative Dermatology, The society for Investigative Dermatology, Inc, Vol. 102, No. 4, pp. 385-389, April 1994), and that hyaluronic acid is hardly detected in the part affected by solar elastosis caused by ultraviolet radiation (Takuo TSUJI, Physiological Aging of Skin: Difference from Photo-aging, Clinical Dermatology, Igaku-Shoin Ltd., Special Edition, vol. 51, no. 5, 53-57, Apr. 15, 1997) and accordingly it is considered that the drying and the deterioration of the vital properties and the elasticity of the skin are caused and consequently wrinkles are increased. For the improvement of such conditions, cosmetics containing hyaluronic acid has been applied to keep the moisture retention capability of the skin surface; however, hyaluronic acid, which is a high molecular weight molecule, is hard to penetrate into the skin, and thus, the fundamental improvement cannot be expected. Accordingly, it is highly expected to develop a substance which can fundamentally improve the skin function by increasing the hyaluronic acid synthesizing capability of the cells by themselves.
Retinoic acid has been known as a hyaluronic acid production-promoting substance in the epidermis. Retinoic acid originally exists in the epidermis and is a substance involved in the proliferation and the differentiation of the epidermal cells. However, retinoic acid has the skin irritation properties. From this point of view, it is desired to find a hyaluronic acid production-promoting substance with which such problems can be avoided.
On the other hand, it has been reported that N-acetylglucosamine, which is a saccharide constituting hyaluronic acid, can promote hyaluronic acid production in the cultured epidermal cells about 1.5-times at a concentration of 5 mmol/L independently from the cell proliferation (Fine Chemical, CMC Co., Ltd., vol. 30, no. 22, 5-11, Dec. 15, 2001). However, a high concentration of N-acetylglucosamine is required to exert the hyaluronic acid production-promoting effect and accordingly, it is desired to develop a material which has an sufficient effect even at lower concentrations in order to apply in the broader fields such as the field of cosmetics and pharmaceuticals.